tonight about the condition of Joan rivers. Hospitalized yesterday when she stopped breathing during a medical procedure. The latest from Linzie Davis. Reporter: An update on the condition of Joan rivers. ABC news has learned the comedienne is unconscious and has been ever since she was rushed to the hospital yesterday after suffering cardiac arrest during a procedure at an endoscopy clinic. Doctors are intentionally keeping the 81-year-old sedated and under close supervision until they're more comfortable with her condition. Her daughter Melissa, by her side tonight saying her mother's "Condition remains serious but she is receiving the best treatment and care possible. We ask that you continue to keep her in your thoughts as we pray for her recovery." Her recovery largely depends on just how long the comedienne was without oxygen. Timing is critical. In cardiac arrest, the heart suddenly stops beating. If oxygen does not get to the brain, it can become severely damaged in just four to six minutes. White it's not clear exactly what kind of procedure rivers was having, over 50 million Americans undergo endoscopy each year. 60% of the complications with this kind of procedure are heart related. Which is why there are very specific guidelines for these types of procedures, including the presence of someone Sert field in basic life support. Just hours before her procedure, rivers was on stage in a new York City theater dong what she loved most, making people laugh. The family says they've received prayers from around the world. And a federal judge siding

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